Atherosclerosis is the leading cause of death in the United States, with 1 in 5 deaths (653,000 annually) attributable to coronary artery disease alone. It is believed that patient risk depends on a variety of factors including lesion structure, biomechanics, and morphological and chemical composition. While many imaging modalities are available for visualizing atherosclerotic plaques, none are capable of providing detailed information about chemical composition, which may be useful for better understanding disease progression and improving patient management. Raman spectroscopy is a nondestructive technique based on spectral analysis of inelastically scattered photons that yields detailed information about molecular composition. Raman spectroscopy in the fingerprint region (400-1800 cm"1) has been demonstrated as a viable technique for plaque diagnosis in ex vivo coronary arteries, but recent studies have shown that the high wavenumber region (>2700 cm"1) offers distinct technical advantages and different diagnostic capability. In this project we will investigate the combined use of fingerprint and high wavenumber Raman spectroscopy in a catheter- based system that is suitable for in vivo human coronary artery plaque diagnosis. [unreadable] [unreadable] [unreadable]